927 resultados para EBT2, EBT3, Gafchromic film, In vivo dosimetry, Radiotherapy
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The ultimate check of the actual dose delivered to a patient in radiotherapy can only be achieved by using in vivo dosimetry. This work reports a pilot study to test the applicability of a thermoluminescent dosimetric system for performing in vivo entrance dose measurements in external photon beam radiotherapy. The measurements demonstrated the value of thermoluminescent dosimetry as a treatment verification method and its applicability as a part of a quality assurance program in radiotherapy. (c) 2009 Elsevier Ltd. All rights reserved.
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Introduo A dosimetria in vivo til na medio da dose administrada aos doentes durante o tratamento, avaliando diferenas significativas entre a dose prescrita e a dose administrada no volume alvo, bem como nos rgos de risco. Objetivo Comparar a dose medida com a dose calculada em doentes com tumores de mama com e sem filtro fsico. Mtodos Realizaram-se medies da dose na pele, utilizando dodos tipop, para os campos tangenciais e respetivos field-in-field em 38 doentes. Resultados Verificaram-se diferenas estatisticamente significativas nos campos tangenciais open (=0,000). Discusso Estudos reportam desvios sistemticos significativos entre a dose calculada e a dose medida. Concluso Com este estudo conclui-se que no existe influncia nas doses devido presena do filtro fsico.
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BACKGROUND AND PURPOSE: A pregnant woman was referred for post-operative radiotherapy of a malignant schwannoma in the head and neck region. A best-treatment plan was devised in order to minimize the fetal dose. MATERIAL AND METHODS: The fetal dose resulting from radiological examinations was determined according to international protocols, that resulting from radiotherapy was calculated according to Recommendation 36 of the American Association of Physicists in Medicine (AAPM) Task Group. Pre-treatment dosimetry was performed with an anthropomorphic phantom. Several alternative treatment plans were evaluated. The use of a multileaf collimator (MLC) and a virtual wedge (VW) was compared to cerrobend blocks (CB) and physical wedge (PW). In-vivo dosimetry was performed using a vaginal probe containing thermoluminescent dosimeters (TLD). RESULTS: The total fetal dose resulting from diagnostic and radiotherapy procedures was estimated to be 36 mGy. The technique based on MLC and VW was elected for patient treatment. Measurements for this configuration resulted in afetal dose reduction of 82%. The shielding of the patient's abdomen further reduced the fetal dose by 42%. CONCLUSION: The use of VW and MLC for the treatment of a pregnant woman is highly recommended. Each case should be individually studied with pre-treatment and in-vivo dosimetry.
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Virtual colonoscopy (VC) is a minimally invasive means for identifying colorectal polyps and colorectal lesions by insufflating a patients bowel, applying contrast agent via rectal catheter, and performing multi-detector computed tomography (MDCT) scans. The technique is recommended for colonic health screening by the American Cancer Society but not funded by the Centers for Medicare and Medicaid Services (CMS) partially because of potential risks from radiation exposure. To date, no invivo organ dose measurements have been performed for MDCT scans; thus, the accuracy of any current dose estimates is currently unknown. In this study, two TLDs were affixed to the inner lumen of standard rectal catheters used in VC, and in-vivo rectal dose measurements were obtained within 6 VC patients. In order to calculate rectal dose, TLD-100 powder response was characterized at diagnostic doses such that appropriate correction factors could be determined for VC. A third-order polynomial regression with a goodness of fit factor of R2=0.992 was constructed from this data. Rectal dose measurements were acquired with TLDs during simulated VC within a modified anthropomorphic phantom configured to represent three sizes of patients undergoing VC. The measured rectal doses decreased in an exponential manner with increasing phantom effective diameter, with R2=0.993 for the exponential regression model and a maximum percent coefficient of variation (%CoV) of 4.33%. In-vivo measurements yielded rectal doses ranged from that decreased exponentially with increasing patient effective diameter, in a manner that was also favorably predicted by the size specific dose estimate (SSDE) model for all VC patients that were of similar age, body composition, and TLD placement. The measured rectal dose within a younger patient was favorably predicted by the anthropomorphic phantom dose regression model due to similarities in the percentages of highly attenuating material at the respective measurement locations and in the placement of the TLDs. The in-vivo TLD response did not increase in %CoV with decreasing dose, and the largest %CoV was 10.0%.
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PURPOSE:<br/>To evaluate the combination of a pressure-indicating sensor film with hydrogel-forming microneedle arrays, as a method of feedback to confirm MN insertion in vivo.<br/>METHODS:<br/>Pilot in vitro insertion studies were conducted using a Texture Analyser to insert MN arrays, coupled with a pressure-indicating sensor film, at varying forces into excised neonatal porcine skin. In vivo studies involved twenty human volunteers, who self-applied two hydrogel-forming MN arrays, one with a pressure-indicating sensor film incorporated and one without. Optical coherence tomography was employed to measure the resulting penetration depth and colorimetric analysis to investigate the associated colour change of the pressure-indicating sensor film.<br/>RESULTS:<br/>Microneedle insertion was achieved in vitro at three different forces, demonstrating the colour change of the pressure-indicating sensor film upon application of increasing pressure. When self-applied in vivo, there was no significant difference in the microneedle penetration depth resulting from each type of array, with a mean depth of 237 m recorded. When the pressure-indicating sensor film was present, a colour change occurred upon each application, providing evidence of insertion.<br/>CONCLUSIONS:<br/>For the first time, this study shows how the incorporation of a simple, low-cost pressure-indicating sensor film can indicate microneedle insertion in vitro and in vivo, providing visual feedback to assure the user of correct application. Such a strategy may enhance usability of a microneedle device and, hence, assist in the future translation of the technology to widespread clinical use.
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In this work, a fast, non destructive voltammetric method for cocaine detection in acetonitrile medium using a platinum disk electrode chemically modified with cobalt-hexacyanoferrate (CoHCFe) film is described. The deposition of CoHCFe film at platinum disk (working electrode) was carried out in aqueous solution containing NaClO(4) at 0.1 mol L(-1) as supporting electrolite. Stability studies of the film and subsequent voltammetric analysis of cocaine were made in acetonitrile medium with NaClO4 at 0.1 mol L(-1) as supporting electrolite. A reversible interaction between cocaine and CoHCFe at the film produces a proportional decrease of original peak current, due to the formation of a complex between cocaine and cobalt ions, with subsequent partial passivation of the film surface, being the intensity of current decrease used as analytical signal for cocaine. A linear dependence of cocaine detection was carried out in the range from 2.4 x 10 x 4 to 1.5 x 10(-3) mol L(-1), with a linear correlation coefficient of 0.994 and a detection limit of 1.4 x 10 x 4 mol L(-1). The analysis of confiscated samples by the proposed method indicated cocaine levels from 37% to 95% (m/m) and these results were validated by comparison to HPLC technique, being obtained good correlation between both methods. (C) 2009 Elsevier Ireland Ltd. All rights reserved.
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In vivo dosimetry is a way to verify the radiation dose delivered to the patient in measuring the dose generally during the first fraction of the treatment. It is the only dose delivery control based on a measurement performed during the treatment. In today's radiotherapy practice, the dose delivered to the patient is planned using 3D dose calculation algorithms and volumetric images representing the patient. Due to the high accuracy and precision necessary in radiation treatments, national and international organisations like ICRU and AAPM recommend the use of in vivo dosimetry. It is also mandatory in some countries like France. Various in vivo dosimetry methods have been developed during the past years. These methods are point-, line-, plane- or 3D dose controls. A 3D in vivo dosimetry provides the most information about the dose delivered to the patient, with respect to ID and 2D methods. However, to our knowledge, it is generally not routinely applied to patient treatments yet. The aim of this PhD thesis was to determine whether it is possible to reconstruct the 3D delivered dose using transmitted beam measurements in the context of narrow beams. An iterative dose reconstruction method has been described and implemented. The iterative algorithm includes a simple 3D dose calculation algorithm based on the convolution/superposition principle. The methodology was applied to narrow beams produced by a conventional 6 MV linac. The transmitted dose was measured using an array of ion chambers, as to simulate the linear nature of a tomotherapy detector. We showed that the iterative algorithm converges quickly and reconstructs the dose within a good agreement (at least 3% / 3 mm locally), which is inside the 5% recommended by the ICRU. Moreover it was demonstrated on phantom measurements that the proposed method allows us detecting some set-up errors and interfraction geometry modifications. We also have discussed the limitations of the 3D dose reconstruction for dose delivery error detection. Afterwards, stability tests of the tomotherapy MVCT built-in onboard detector was performed in order to evaluate if such a detector is suitable for 3D in-vivo dosimetry. The detector showed stability on short and long terms comparable to other imaging devices as the EPIDs, also used for in vivo dosimetry. Subsequently, a methodology for the dose reconstruction using the tomotherapy MVCT detector is proposed in the context of static irradiations. This manuscript is composed of two articles and a script providing further information related to this work. In the latter, the first chapter introduces the state-of-the-art of in vivo dosimetry and adaptive radiotherapy, and explains why we are interested in performing 3D dose reconstructions. In chapter 2 a dose calculation algorithm implemented for this work is reviewed with a detailed description of the physical parameters needed for calculating 3D absorbed dose distributions. The tomotherapy MVCT detector used for transit measurements and its characteristics are described in chapter 3. Chapter 4 contains a first article entitled '3D dose reconstruction for narrow beams using ion chamber array measurements', which describes the dose reconstruction method and presents tests of the methodology on phantoms irradiated with 6 MV narrow photon beams. Chapter 5 contains a second article 'Stability of the Helical TomoTherapy HiArt II detector for treatment beam irradiations. A dose reconstruction process specific to the use of the tomotherapy MVCT detector is presented in chapter 6. A discussion and perspectives of the PhD thesis are presented in chapter 7, followed by a conclusion in chapter 8. The tomotherapy treatment device is described in appendix 1 and an overview of 3D conformai- and intensity modulated radiotherapy is presented in appendix 2. - La dosimtrie in vivo est une technique utilise pour vrifier la dose dlivre au patient en faisant une mesure, gnralement pendant la premire sance du traitement. Il s'agit de la seule technique de contrle de la dose dlivre base sur une mesure ralise durant l'irradiation du patient. La dose au patient est calcule au moyen d'algorithmes 3D utilisant des images volumtriques du patient. En raison de la haute prcision ncessaire lors des traitements de radiothrapie, des organismes nationaux et internationaux tels que l'ICRU et l'AAPM recommandent l'utilisation de la dosimtrie in vivo, qui est devenue obligatoire dans certains pays dont la France. Diverses mthodes de dosimtrie in vivo existent. Elles peuvent tre classes en dosimtrie ponctuelle, planaire ou tridimensionnelle. La dosimtrie 3D est celle qui fournit le plus d'information sur la dose dlivre. Cependant, notre connaissance, elle n'est gnralement pas applique dans la routine clinique. Le but de cette recherche tait de dterminer s'il est possible de reconstruire la dose 3D dlivre en se basant sur des mesures de la dose transmise, dans le contexte des faisceaux troits. Une mthode itrative de reconstruction de la dose a t dcrite et implmente. L'algorithme itratif contient un algorithme simple bas sur le principe de convolution/superposition pour le calcul de la dose. La dose transmise a t mesure l'aide d'une srie de chambres ionisations alignes afin de simuler la nature linaire du dtecteur de la tomothrapie. Nous avons montr que l'algorithme itratif converge rapidement et qu'il permet de reconstruire la dose dlivre avec une bonne prcision (au moins 3 % localement / 3 mm). De plus, nous avons dmontr que cette mthode permet de dtecter certaines erreurs de positionnement du patient, ainsi que des modifications gomtriques qui peuvent subvenir entre les sances de traitement. Nous avons discut les limites de cette mthode pour la dtection de certaines erreurs d'irradiation. Par la suite, des tests de stabilit du dtecteur MVCT intgr la tomothrapie ont t effectus, dans le but de dterminer si ce dernier peut tre utilis pour la dosimtrie in vivo. Ce dtecteur a dmontr une stabilit court et long terme comparable d'autres dtecteurs tels que les EPIDs galement utiliss pour l'imagerie et la dosimtrie in vivo. Pour finir, une adaptation de la mthode de reconstruction de la dose a t propose afin de pouvoir l'implmenter sur une installation de tomothrapie. Ce manuscrit est compos de deux articles et d'un script contenant des informations supplmentaires sur ce travail. Dans ce dernier, le premier chapitre introduit l'tat de l'art de la dosimtrie in vivo et de la radiothrapie adaptative, et explique pourquoi nous nous intressons la reconstruction 3D de la dose dlivre. Dans le chapitre 2, l'algorithme 3D de calcul de dose implment pour ce travail est dcrit, ainsi que les paramtres physiques principaux ncessaires pour le calcul de dose. Les caractristiques du dtecteur MVCT de la tomothrapie utilis pour les mesures de transit sont dcrites dans le chapitre 3. Le chapitre 4 contient un premier article intitul '3D dose reconstruction for narrow beams using ion chamber array measurements', qui dcrit la mthode de reconstruction et prsente des tests de la mthodologie sur des fantmes irradis avec des faisceaux troits. Le chapitre 5 contient un second article intitul 'Stability of the Helical TomoTherapy HiArt II detector for treatment beam irradiations'. Un procd de reconstruction de la dose spcifique pour l'utilisation du dtecteur MVCT de la tomothrapie est prsent au chapitre 6. Une discussion et les perspectives de la thse de doctorat sont prsentes au chapitre 7, suivies par une conclusion au chapitre 8. Le concept de la tomothrapie est expos dans l'annexe 1. Pour finir, la radiothrapie informationnelle 3D et la radiothrapie par modulation d'intensit sont prsentes dans l'annexe 2.
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Radioimmunodetection of tumours with monoclonal antibodies is becoming an established procedure. Positron emission tomography (PET) shows better resolution than normal gamma camera single photon emission tomography and can provide more precise quantitative data. Thus, in the present study, these powerful methods have been combined to perform radioimmuno PET (RI-PET). Monoclonal antibodies directed against carcinoembryonic antigen (CEA) an IgG, its F(ab')2 and a mouse-human chimeric IgG derived from it were labelled with 124I, a positron-emitting radionuclide with a convenient physical half-life of four days. Mice, xenografted with a CEA-producing human colon carcinoma, were injected with the 124I-MAb and the tumours were visualized using PET. The concentrations of 124I in tumour and normal tissue were determined by both PET and direct radioactivity counting of the dissected animals, with very good agreement. To allow PET quantification, a procedure was established to account for the presence of radioactivity during the absorption correction measurement (transmission scan). Comparison of PET and tissue counting indicates that this novel combination of radioimmunolocalization and PET (RI-PET) will provide, in addition to more precise diagnosis, more accurate radiation dosimetry for radioimmunotherapy.
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BACKGROUND AND PURPOSE: The EORTC 22043-30041 trial investigates the role of the addition of androgen suppression to post-operative radiotherapy in patients who have undergone radical prostatectomy. As part of the quality assurance of radiotherapy (QART) a Dummy Run (DR) procedure was performed. MATERIALS AND METHOD: The protocol included detailed and published delineation guidelines. Participating institutions digitally submitted radiotherapy treatment volumes and a treatment plan for a standard clinical case. Submissions were centrally reviewed using the VODCA software platform. RESULTS: Thirty-eight submissions from thirty-one institutions were reviewed. Six were accepted without comments. Twenty-three were accepted with comments on one or more items: target volume delineation (22), OAR delineation (23), planning and dosimetry (3) or treatment verification (1). Nine submissions were rejected requiring resubmission, seven for target volume delineation reasons alone. Intervention to highlight the importance of delineation guidelines was made prior to the entry of the first patient in the trial. After this, a lower percentage of resubmissions was required. CONCLUSIONS: The EORTC 22043-30041 Dummy Run highlights the need for timely and effective QART in clinical trials. The variation in target volume and OAR definition demonstrates that clinical guidelines and radiotherapy protocols are not a substitute for QART procedures. Early intervention in response to the Dummy Run improved protocol understanding.
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CONTEXTUALIZAO: O Ultrassom (US) um dos recursos fsicos amplamente utilizado e pesquisado nos tratamentos de fisioterapia. Sabe-se que diante de uma escassa literatura sobre efeitos do US em tecidos sadios, muitos profissionais fisioterapeutas acabam realizando aplicaes infundadas de mtodos e parmetros. OBJETIVO: Avaliar possveis alteraes histolgicas e morfomtricas do tecido sadio in vivo de ratos Wistar irradiados com diferentes intensidades de US. MTODOS: Trinta ratos da linhagem Wistar, distribudos aleatoriamente em cinco grupos de seis animais cada foram tratados na regio dorsal do lado direito numa rea de 4cm. O lado esquerdo serviu como controle. O tratamento foi feito durante quatro dias com 2 minutos de irradiao. Verificou-se a intensidade de sada com dosmetro de preciso antes das aplicaes. Analisou-se a histologia e a morfometria por meio do software Image Tool. RESULTADOS: Observou-se um discreto infiltrado inflamatrio e adelgaamento das fibras da derme, principalmente dos grupos irradiados com 1.5 e 2W/cm. Notou-se tambm um aumento na espessura da epiderme nas amostras dos animais irradiados. Para avaliar os resultados quantitativos, utilizou-se como anlise estatstica ANOVA one way e o teste post hoc de Tukey. Na espessura da epiderme, obtiveram-se diferenas significativas entre grupo controle e os grupos irradiados com 1.0, 1.5 e 2.0W/cm. CONCLUSO: Sob ao do US nas doses maiores houve alteraes na epiderme e derme, respectivamente, o aumento da espessura e proliferao com adelgaamento das fibras colgenas, o que alerta para possveis implicaes do uso do US em esttica.
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In vivo determination of the incorporated activity of Tc-99(m)-MDP (methylene diphosphonate) in bone tissue by means of a scintillation camera requires calibration of the device. This can be carried out by using an anthropomorphic physical phantom. In this work, a new human tibia and fibula phantom is presented to estimate incorporated activity to bone tissue. A tibia and a fibula, taken from a real skeleton, were used to develop the phantom. Images were acquired of the legs of 65 volunteers at different times of incorporation (minimum of 120 and maximum of 2500 min after injection) and count rates of such a region were obtained by means of a computer program. The calibration factor obtained was then used to assess the activity in the two bents. The final result is 0.4995 kBq per cpm for technetium. The proposed method can be used both for radiation protection purposes and for metabolism studies.
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Ps-graduao em Odontologia Restauradora - ICT
